Airplane mode is not sufficient. You have to switch off Bluetooth on your iPhone in Settings, not Control Center.
Is this just for LTE? I upgraded to a GPS only S6. Do I need to keep turning off Bluetooth? (DC Rainmaker seemed to indicate no.)
Guess this is valid for all Apple Watch models. Can you point me to the statement of DCR? Asking because I just read somewhere where he exactly stated the opposite, paraphrased: "of course I leave my iPhone at home to avoid GPS being taken from iPhone".
Edit: found it:
While I already posted earlier this week on the new features of the Apple Watch Series 6, I figured I’d share some quick first run Friday data for ya. As well as some initial thoughts on the handful of other
www.dcrainmaker.com
Let me clarify something about the iphone Airplane mode that's not necessarily obvious.
The default Airplane mode shuts off bluetooth and wifi. That will break the connection to the watch.
However, Airplane mode
remembers if you've previously turned on bluetooth and/or wifi when in Airplane mode and will go back to those settings.
So... when you turn on Airplane mode bluetooth may or may not be active depending on how you had it set when you were last in Airplane mode. Once you do turn off bluetooth within Airplane mode it will remain off for future instances of Airplane mode (unless you turn it back on while in Airplane mode).
As for going to Settings->Bluetooth I don't see the point since the On/Off value there follows the Control Center setting. Try it yourself while on the Settings page.
Now with the above clarified... If you go for a run and the watch can talk to the phone, it will use the phone's GPS instead of the watch's GPS. You can either break the phone/watch connection by going into airplane mode / turning off bluetooth - or you can leave the phone behind and run with just the watch.
Also - be cautious drawing conclusions from differences between small numbers of runs on different days and different times. GPS satellites are not geosynchronous, they're in about a 12 hour orbit. Day to day, or even different times of day, will affect how many satellites are above the horizon and how high in the sky they are. This affects how accurate GPS device positioning will be -- especially if satellites are low on the horizon and their radio signals are affected by trees and building.
Nominally GPS accuracy for a phone or watch is going to be anywhere within a
16ft radius. So imagine going for a walk with a hyperactive puppy on a 16ft leash and plotting his position every so often as he finds different things to sniff and mark. That's going to be a pretty rough plot. Thus the software in the watches and such usually applies a bit of smoothing to the plots. Those smoothing algorithms can vary in how well they do.
Also note that the satellite and road maps provided by Google and so on aren't necessarily dead-on accurate. I haven't found a source saying what level of inaccuracy they have, but common sense suggests there will be some degree of inaccuracy. Perhaps enough to put your otherwise ideal GPS track on the wrong side of the road.
Generally I take GPS tracks and mapping to be a best-estimate and just not worry about bits of wonkiness here and there. I'm also not a competitive runner, so I'm not sussed if two watches show a slightly different distance or if the track shows me going through peoples yards instead of being on the sidewalk or road.
Edit - info from Apple on Airplane Mode
You can use Airplane Mode to turn off the wireless features on your device while you're flying in an airplane.
support.apple.com
